A resistor is a component of a circuit that resists the flow of electrical current. It has two terminals across which electricity must pass, and it is designed to drop the voltage of the current as it flows from one terminal to the other. Resistors are primarily used to create and maintain known safe currents within electrical components.
Resistors are coated with paint or enamel, or covered in molded plastic to protect them. Because they are often too small to be written on, a standardized color-coding system is used to identify them. The first three colors represent ohm value, and a fourth indicates the tolerance, or how close by percentage the resistor is to its ohm value. This is important for two reasons: the nature of its construction is imprecise, and if used above its maximum current, the value can change or the unit itself can burn up.
In physics, resistance is defined as the ability of a substance to prevent or resist the flow of electrical current. A substance resists electrical current because of a collision between electrons and atoms, which slows the electrons down and converts some of their energy to heat energy. In some cases, the energy is also converted into light.
German physicist Georg Ohm (1789-1854) is credited with discovering the effect of a material's make up, length and thickness on its resistance. In fact, the standard unit of measuring resistance, the ohm, is named after him. Ohm's law became publicly known in 1827 and states that a circuit’s resistance is 1 ohm if a 1-volt voltage make 1 amp of current. According to Ohm's law, a circuit's resistance is equal to its voltage divided by the amount of current.
The measure of the potential electrical resistance of a conductive material. It is determined experimentally using the equation [pic] = RA/l, where R is the...